WO2013100742A1

WO2013100742A1 - Fiber-optic sensor device

Info

Publication number: WO2013100742A1
Application number: PCT/KR2012/011861
Authority: WO
Inventors: 반재경; 최상진
Original assignee: 전북대학교산학협력단
Priority date: 2011-12-29
Filing date: 2012-12-31
Publication date: 2013-07-04
Also published as: US20140299753A1; KR101280922B1; US9170130B2

Abstract

Provided is a fiber-optic sensor device. The fiber-optic sensor device is capable of sensing a change in physical quantity by using two fiber Bragg grating units arranged within an optical fiber and a fiber-optic sensor unit arranged therebetween, thereby implementing a low cost fiber-optic grating sensor having a simple structure without requiring a reference FBG.

Description

【Specification】

[Name of invention]

Fiber optic sensor

Technical Field

The present invention relates to an optical fiber sensor device, and more particularly, to an optical fiber sensor device for sensing a physical quantity using an optical fiber Bragg grating.

Background Art

Optical gratings, which are widely used for optical communication and optical fiber sensors, are generally made by a change in refractive index in the optical fiber core generated by irradiating a strong ultraviolet laser to the optical fiber.

<3> At this time, it is classified into short period optical fiber grating and long period optical fiber grating according to the characteristics of refractive index modulation cycle of generated optical fiber, and has been researched and used as reflection and transmission filter according to wavelength according to their characteristics. .

In addition, the fiber Bragg grating induced a change in the axial refraction in the fiber core. The optical fiber grating reflects only light with a narrow line width (typically 0.1 to Inm) at the center of the Bragg wavelength that satisfies Bragg conditions, and passes the light of the remaining wavelengths. This Bragg wavelength changes as the temperature of the fiber Bragg grating changes or when a stress is applied. Therefore, many optical fiber grating sensors have been developed that use this property to measure temperature, strain and pressure.

However, fiber optic grating sensors require expensive reference Fiber Bragg Grating (FBG), which is expensive and complicated in structure. Accordingly, there is a need for a search for a method for implementing a low cost simple structured fiber grating sensor.

[Detailed Description of the Invention]

[Technical problem]

The present invention has been made to solve the above problems, and an object of the present invention is to detect a change in physical quantity by using two optical fiber Bragg grating portion disposed in the optical fiber and the optical fiber sensor portion disposed therebetween. It is to provide an optical fiber sensor device.

Technical Solution

<7> To achieve the above object ^. According to one embodiment of the present invention, an optical fiber sensor device includes a light source for generating light; An optical fiber to which light generated by the light source is incident; The light A first optical fiber Bragg grating portion disposed in the fiber and reflecting a portion of the light generated by the light source; An optical fiber sensor unit disposed in the optical fiber and changing an intensity of light passing through the first optical fiber Bragg grating unit based on a specific physical quantity; A two-fiber Bragg grating portion disposed in the optical fiber and reflecting a portion of the light passing through the optical fiber sensor portion; And a monitoring unit configured to sense the specific physical quantity changed in the optical fiber sensor unit based on a ratio of the light intensity of the reflected light reflected by the first optical fiber Bragg grating unit and the reflected light reflected by the second optical fiber Bragg grating unit. .

The monitoring unit may include: a filter unit configured to selectively pass first reflected light reflected from the first optical fiber Bragg grating unit and second reflected light reflected from the second optical fiber Bragg grating unit; A photoelectric conversion element converting the first reflected light and the second reflected light passing through the filter into a first electric signal and a second electric signal, respectively; And calculating the ratio of the light intensity of the first reflected light and the second reflected light using the first electric signal and the second electric signal, and changing the specificity changed in the optical fiber sensor unit based on the ratio of the light intensity. It may include a signal processor for detecting the physical quantity.

In addition, the filter unit may be a variable Fabry-Perot (F-P) filter for selectively passing light having a specific wavelength according to a bias voltage.

<ιο> And the photoelectric conversion element, a photodiode that converts light into an electrical signal

(photo diode) may be used.

<ιι> Further, the Bragg reflection wavelength characteristics may be different from each other in the first optical fiber Bragg grating portion and the second optical fiber Bragg grating portion.

In addition, the optical fiber sensor unit may be an intensity-type optical fiber sensor that changes and outputs the intensity of incident light according to a specific physical quantity.

In addition, the optical fiber, n (n is a natural number) of the optical fiber Bragg grating portion, and includes n-1 optical fiber sensor unit disposed between each of the n optical fiber Bragg grating portion, the monitoring The specific physics changed in the optical fiber sensor section disposed between the two neighboring optical fiber Bragg grating sections based on the ratio of the light intensities of the two reflected light reflected by the two neighboring optical fiber Bragg grating sections in the optical fiber. Volume can be detected.

<| 4> The optical fiber may have m pieces (m is a natural number), and may further include a wavelength division multiplexer that splits the light incident from the light source into wavelengths and enters the m optical fibers, respectively.

<15> Advantageous Effects

According to various embodiments of the present disclosure, it is possible to provide an optical fiber sensor device for detecting a change in physical quantity using two optical fiber Bragg grating portions disposed in an optical fiber and an optical fiber sensor portion disposed therebetween. Also, it is possible to implement a low cost, simple structure fiber grating sensor that does not require a reference FBG.

[Brief Description of Drawings]

1 is a view showing an optical fiber sensor device according to an embodiment of the present invention;

FIG. 2 is a diagram illustrating a case of an optical fiber sensor device including a plurality of optical fiber Bragg gratings and a plurality of optical fiber sensor units according to an embodiment of the present invention.

<19>

[Form for implementation of invention]

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 is a diagram illustrating an optical fiber sensor device 100 according to an embodiment of the present invention. As shown in FIG. 1, the optical fiber sensor device 100 includes a light source 110, a first optical fiber Bragg grating 120, a second optical fiber Bragg grating 125, an optical fiber sensor unit 130, and a monitoring unit ( 140).

The light source 110 includes all optical fiber Bragg gratings (FBG) included in the optical fiber sensor device 100.

Fiber Bragg Grating) generates a wide band of light that includes all of the reflected wavelength band. Then, the light source 110 injects the generated light into the optical fiber 115 through the circler 150 (drculator).

The light generated by the light source 110 is incident to the optical fiber 115. And Fiber Optics (115)

The crab 1 optical fiber Bragg grating part 120, the 2nd optical fiber Bragg grating part 125, and the optical fiber sensor part 130 are arrange | positioned inside.

The first optical fiber Bragg grating portion 120 is disposed in the optical fiber 115 and reflects a part of the light generated by the light source 110. The first reflected light reflected by the first optical fiber Bragg grating unit 120 is incident to the monitoring unit 140 through the circler 150.

The optical fiber sensor unit 130 is disposed in the optical fiber 115 and changes the intensity of light passing through the giant U optical fiber Bragg grating portion based on the specific physical quantity. Specifically, the optical fiber sensor unit 130 is an intensity type optical fiber sensor that changes and outputs the intensity of incident light according to a specific physical quantity. Therefore, when a specific physical quantity is applied to the optical fiber sensor unit 130, the optical fiber sensor changes the intensity of the incident light and outputs the light. Specifically, the optical fiber sensor unit 130 is applied voltage, current, temperature, pressure, strain, turnover, sound, gas concentration The intensity of the incident light is varied according to the output.

The second optical fiber Bragg grating part 135 is disposed in the optical fiber 115 and reflects a part of the light passing through the optical fiber sensor part 130. The second reflected light reflected from the second optical fiber Bragg grating unit 135 passes through the optical fiber sensor unit 130 and the first optical fiber Bragg grating unit 120 to the monitoring unit 140 through the circler 150. Incident.

At this time, the first optical fiber Bragg grating portion 120 and the second optical fiber Bragg grating portion 125 have a Bragg reflection wavelength characteristic _. Are different. Therefore, the first reflected light and the second reflected light are different in wavelength from each other.

The monitoring unit 140 is based on the ratio of the light intensity of the first reflected light reflected by the first optical fiber Bragg grating unit 120 and the second reflected light reflected by the second optical fiber Bragg grating unit 125. The sensor unit 130 detects a specific physical quantity changed or applied. As shown in FIG. 1, the monitoring unit 140 includes a filter unit 142, a photoelectric conversion element 144, and a signal processing unit 146.

The filter unit 142 may include the first reflected light and the second reflected light from the first optical fiber Bragg grating unit 120.

The second light reflected by the optical fiber Bragg grating portion 125 is selectively passed. To this end, the filter unit 142 is used a variable Fabry-Perot (F-P) filter that selectively passes the light of a specific wavelength in accordance with the bias voltage. Therefore, since the first reflected light and the second reflected light have different wavelengths, the filter unit 142 can pass the first reflected light and the second reflected light separately.

The photoelectric conversion element 144 converts the first and second reflected light passing through the filter unit 142 into first and second electric signals, respectively. To this end, a photodiode for converting light into an electrical signal is used as the photoelectric conversion element 144.

The signal processor 146 receives the first electrical signal and the crab 2 electrical signal. Then, the signal processing unit 146 calculates the ratio of the light intensity of the first reflected light and the second reflected light using the electric signal and the second electric signal, and changes the optical signal at the optical fiber sensor unit 130 based on the ratio of the light intensity. Detected specific physical quantity.

The optical fiber sensor device 100 having such a structure has a measurable self-reference characteristic even when the light source generates output change over a short time or a long time by using a ratio of light reflected from two optical fiber Bragg gratings. This self-reference property does not require an expensive reference fiber Bragg grating and enables the implementation of the optical fiber-based optical fiber sensor device 100 having a relatively simple structure.

The signal processing unit 146 and the first reflected light reflected from the first optical fiber Bragg grating unit 120 and A process of sensing the physical quantity changed in the optical fiber sensor unit 130 using the ratio of the second reflected light reflected by the second optical fiber Bragg grating unit 125 will be described below.

As shown in FIG. 1, the first optical fiber Bragg grating portion 120 and the second optical fiber Bragg grating portion 125 have reflectances R _u and R ₁₂ , respectively, and the conditions of the optical fiber sensor device 100. Bragg reflection wavelength characteristics (center wavelength and full wavelength at half maximum (FWHM)).

Looking at the operation principle, the light emitted from the light source 110 proceeds from the port ① to the port ② through the optical circler 150 and is incident to the optical fiber 115. The incident light is reflected from the first optical fiber Bragg grating unit 120 to the first reflected light corresponding to the Bragg reflection wavelength, and the light of the other wavelengths is formed by the first optical fiber Bragg grating unit 120 and the optical fiber sensor unit 130. After passing, the second optical fiber Bragg grating portion 125 is reached. The second reflected light having a wavelength corresponding to the Bragg reflected wavelength of the second optical fiber Bragg grating part 125 is reflected by the second optical fiber Bragg grating part 125 and passes through the optical fiber sensor part 130 to the optical circler 150. Enters port ③ by The second reflected light emitted from the port ③ is reflected by the first reflected light reflected by the first optical fiber Bragg grating part 120 and the second optical fiber Bragg grating part 125 according to the bias voltage input to the filter part 142. Divided into second reflected light. The first reflected light and the second reflected light are converted into a first electrical signal and a second electrical signal by the photoelectric conversion element 144.

Since the monitoring unit 140 is at a short distance, the optical fiber loss between the light source 110, the optical circler 150, the optical circler 150, the filter unit 142, and the photoelectric conversion element 144 is ignored. . Under this assumption, the optical power Pu of the first reflected light reflected by the first optical fiber Bragg grating portion 120 and incident on the photoelectric conversion element 144 may be expressed by Equation (1) below.

2

_<37> P \ ⁼ Pin · ^ -2 · ^ fiberl · ^ ll · ^ 62—3 · ^ fp ⁽¹⁾

Where Ρ _ίπ is the input optical power, K _cl - ₂ : loss that occurs when proceeding from the optical _circler 150 port ① to the port ②, K _fiberl : the optical _circler port 150 and the first optical fiber loss between the Bragg grating (120), R _u: first reflectivity of the fiber Bragg grating _{_{(120), K C2 - 3}} : the light standing Klee data 150 loss that occurs when going from port ② a port ③, K _fp: This is a loss of the variable F-P filter portion 142.

In addition, under the same assumption, the optical power _{12 12} of the second reflected light reflected from the second optical fiber Bragg grating 125 and incident on the photoelectric conversion element 144 may be represented by Equation (2).

Where K _fiber2 : loss between the first optical fiber Bragg grating 120 and the second optical fiber Bragg grating 125, K _FBG11 : loss depending on the transmission spectrum of the first optical fiber Bragg grating 120, R ₁₂ : 2 reflectance of the optical fiber Bragg grating 125, H _u : transfer function of the optical fiber sensor unit 130 S _u .

Using Equation (1) and Equation (2), we can define the measurement parameters:

It is a calibration factor. Since H _u can be obtained from X _u , the physical quantity can be calculated from Eq. (3) if the ratio of light intensity changes. In addition, the bias voltage of the variable FP filter unit 142 that passes the wavelength corresponding to the reflected wavelength of the first optical fiber Bragg grating 120 is referred to as V _fpll , and the first optical fiber Bragg _grating 120 is changed due to temperature change. when the reflection wavelength of the variable byeonhaeteul FP filter 142 when referred to as the bias voltage changes ^Α ιι, all be located above the reflection wavelength of the first fiber Bragg grating 120, the variable filter FP unit 142 in the By measuring the maximum output at bias voltage ^{l 1} = ^V P ^{u + A} ^V _u as p _u , the change in the optical fiber Bragg grating reflection wavelength due to temperature change does not affect the measurement result. .

Even if the intensity of the input light is changed and the temperature is changed and the optical fiber Bragg grating reflection wavelength is changed, H _u by Equation (3) derived from Equations (1) and (2) is constant. By such a principle, the optical fiber sensor device 100 according to the present embodiment can detect a change in physical quantity generated in the optical fiber sensor unit 130. In addition, according to the present embodiment, the optical fiber sensor device 100 does not require an expensive reference optical fiber Bragg grating, which is required in the conventional wavelength-based fiber Bragg grating sensor structure, and can measure the input light regardless of the change in the input light or the temperature change. This has the advantage of reducing the cost of implementing an interrogator.

Hereinafter, referring to FIG. 2, a plurality of optical fiber Bragg gratings and a plurality of optical fibers The case where the sensor unit is included will be described. FIG. 2 is a diagram illustrating an optical fiber sensor device including a plurality of optical fiber Bragg gratings and a plurality of optical fiber sensor units in the measuring unit 410, according to an exemplary embodiment. Compared to FIG. 1, the optical fiber sensor device 200 of FIG. 2 includes a plurality of optical fiber Bragg gratings and a plurality of optical fiber sensor parts in the measuring unit 410, and the optical fiber sensor device 200 includes a wavelength division multiplexer 420 for each optical fiber. You can see that it is multiplexed.

Specifically, as shown in FIG. 2, each optical fiber constitutes one row

And n n optical fiber Bragg grating parts, and _n ᅳ 1 optical fiber sensor parts disposed between each of the n optical fiber Bragg grating parts. Where n is a natural number.

Then, the monitoring unit 140 is an optical fiber sensor disposed between two neighboring optical fiber Bragg grating portion based on the ratio of the light intensity of the two reflected light reflected by two adjacent optical fiber Bragg grating portion in the optical fiber. The unit detects a specific physical quantity that has changed.

<5i> In addition, m optical fibers (Hi is a natural number), wavelength division multiplexer 420 is a light source 110

The light incident on the beam is divided into wavelengths and then incident on the m optical fibers. Here, the wavelength division multiplexer 420 determines the division unit of the wavelength according to the reflection wavelength band of all of the optical fiber Bragg gratings included in each optical fiber.

In addition, all of the plurality of optical fiber Bragg gratings included in the measuring unit 410 may have different Bragg reflection characteristics.

As such, the optical fiber sensor device 200 including the plurality of optical fiber Bragg gratings and the plurality of optical fiber measuring units may detect a change in physical quantity in a wide area.

In addition, the optical fiber sensor device 100 may be far apart because the monitoring unit 140 and the optical fiber sensor unit 130 are connected by using the optical fiber 115, and are separated and paralleled by a wavelength division multiplexer. Since each measurement point multiplexed by X can have different lengths, there is no restriction of the distance between the monitoring point and the measurement point.

In addition, as shown in FIG. 2, the optical intensity-based optical fiber sensor units are located between two optical fiber Bragg gratings, and each calibration factor is measured through Equation (3). ) To obtain the physical quantity generated in the light intensity based optical fiber sensor part, and m * (n-1) light intensity based optical fiber sensor parts can be arranged, so that multiple points can be measured at the same time.

And a light intensity based fiber optic sensor located between the two fiber Bragg gratings. By changing the western structure according to the physical quantity to be measured, the user can measure the desired physical quantity and the sensitivity can be appropriately adjusted according to the structure of the optical fiber sensor unit.

In addition, since the light intensity-based optical fiber sensor unit located between the two optical fiber Bragg gratings is composed of optical fibers, the user can adjust the measurement range to the desired measurement range without limiting the length of the portion to be measured from the point sensor to the distributed sensor.

In addition, while the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific embodiments described above, but the present invention without departing from the gist of the present invention claimed in the claims. Various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention. Industrial Applicability

The present invention is applicable to the optical fiber sensor device industry as a sensor device for sensing a physical quantity using an optical fiber Bragg grating.

<6 ()>

Claims

[Range of request]

[Claim 1]

A light source for generating light;

An optical fiber to which light generated by the light source is incident;

A first optical fiber Bragg grating portion disposed in the optical fiber and reflecting a portion of the light generated by the light source;

An optical fiber sensor unit disposed in the optical fiber and changing an intensity of light passing through the first optical fiber Bragg grating unit based on a specific physical quantity;

A second optical fiber Bragg grating part disposed in the optical fiber and reflecting a part of the light passing through the optical fiber sensor part; And

And a monitoring unit configured to sense the specific physical quantity changed in the optical fiber sensor unit based on a ratio of light intensities of the reflected light reflected by the first optical fiber Bragg grating unit and the reflected light reflected by the second optical fiber Bragg grating unit. Fiber optic sensor. [Claim 21]

The method of claim 1,

The monitoring unit,

A filter unit selectively passing the first reflected light reflected from the first optical fiber Bragg grating unit and the second reflected light reflected from the second optical fiber Bragg grating unit;

A photoelectric conversion element for converting the first reflected light and the second reflected light passing through the filter unit into a first electric signal and a second electric signal, respectively; And

The ratio of the light intensity between the first reflected light and the second reflected light is calculated using the first electrical signal and the second electrical signal, and the specific physical quantity changed in the optical fiber sensor unit is calculated based on the ratio of the light intensity. And a signal processing unit for sensing.

[Claim 3]

The method of claim 2,

The filter unit

Optical fiber sensor device, characterized in that the variable Fabry-Perot (F-P) filter for selectively passing light of a specific wavelength in accordance with the bias voltage.

[Claim 4]

The method of claim 2,

The photoelectric conversion element, An optical fiber sensor device, comprising: a photodiode for converting light into an electrical signal.

[Claim 5]

The method of claim 1,

The first optical fiber Bragg grating portion and the second optical fiber Bragg grating portion, the optical fiber sensor characterized in that the Bragg reflection wavelength characteristics are different from each other.

The method of claim 1,

The optical fiber sensor unit,

Optical fiber sensor device characterized in that the intensity type optical fiber sensor for outputting by changing the intensity of the incident light according to a specific physical quantity.

[Claim 7]

In that U term,

The optical fiber,

n-fiber (n is a natural number) including a fiber Bragg grating portion, and n-1 optical fiber sensor portion disposed between each of the n fiber Bragg grating portion,

The monitoring unit,

Detecting the specific physical quantity changed in the optical fiber sensor portion disposed between the two neighboring optical fiber Bragg grating portions based on the ratio of the light intensities of the two reflected light reflected by the two neighboring optical fiber Bragg grating portions in the optical fiber; Optical fiber sensor device, characterized in that.

[Claim 8]

The method of claim 7,

The optical fiber is m (m is a natural number),

And a wavelength division multiplexer for dividing the light incident from the light source for each wavelength to be incident on the m optical fibers, respectively.